A LEADING wildlife charity has joined the chorus of protests against a 10-mile concrete barrage across the Severn estuary to generate renewable power.

A handful of schemes are being considered by the Government for the Severn estuary, which has enough power locked within its tides to generate 5 per cent of the UK's energy needs.

If a tidal scheme came to pass, it would be the world's largest-ever green energy project.

In January, Energy Secretary Ed Miliband announced a shortlist of five advanced schemes which had met the Government's criteria, including a controversial barrage from Cardiff to Weston-super-Mare.

Now, for the first time, the Wildlife Trusts has joined the Royal Society for the Protection of Birds (RSPB) in calling on the Department of Energy and Climate Change to ditch the Cardiff-Weston idea.

The trust says it would cause "catastrophic environmental damage at huge public expense".

The charity is urging its members, 21,000 of which are in Somerset, to voice their opinions before the public consultations ends on Thursday, April 23.

Opponents fear for the estuary's inter-tidal habitats, fish such as the shad, European eel and salmon, and the migratory birds such as 7,000 geese which descend on the muddy banks each year.

Lisa Schneidau, of Somerset Wildlife Trust, said: "The Severn estuary is internationally recognised and protected for its huge areas of mudflat and saltmarsh, bird populations, migratory fish and geomorphological features.

"The rich diversity of wildlife associated with the Severn estuary is a result of the dynamic nature of the estuary, with the second largest tidal range in the world.

"All five shortlisted energy schemes would have a significant environmental impact, but the Cardiff-Weston barrage would be the most damaging, causing loss of 20,000 hectares of mudflat and saltmarsh, and possible extinction of migratory fish."

She went on: "It would produce the most electricity of the five published options, but it would need tens of billions of pounds of public money in order to be viable.

"The Cardiff-Weston barrage is being promoted most heavily by engineering and most commercial interests."

Half-a-million-pounds of public money has been ring-fenced for two other unproven schemes – a "reef" and a "fence". The tidal "reef", the brainchild of Cornishman Rupert Armstrong-Evans, is the only Severn energy proposition to have secured the full backing of the environmental lobby, and has been given the thumbs-up by engineering experts Atkins.

It is popular because the design started by considering the "crown jewels", factors most likely to prevent a tidal scheme from getting the go-ahead.

Most acutely, this includes the possible loss of thousands of hectares of natural habitat, the impact on fish and the costly time delays to ships travelling into Bristol port.

Somerset Wildlife Trust said the "reef" was an "interesting possibility".

Ms Schneidau said: "It could potentially generate even more energy than a Cardiff-Weston barrage, but with much less environmental damage."

The Wildlife Trusts, in common with the RSPB, broadly supports renewable technology. The RSPB has even recently called for a significant increase in the number of wind farms built onshore in the UK, despite fears over the damage to the countryside.

Nonetheless, the RSPB, which also supports the reef, has described the Cardiff-Weston barrage as an "environmental monster", indicative of how divisive the Severn tidal scheme is proving to be.